Research On Status Evaluation Method For Smart Substation Secondary System

Born with the smart grid concept, smart substation is an important basis and support for the development of smart grid, and as the hub of smart grid, the running state of smart substation secondary system is directly related to the large power grids’ security and stability. Simultaneously with the deepening and application of electrical equipment condition based maintenance, an urgent need to expand exploration and research of status evaluation for smart substation secondary system.However, compared to conventional substation secondary system, there is big difference between system structure and constituent component of smart substation secondary system, which is based on new IEDs and IEC61850 standard and ethernet communication technology. Present status evaluation of secondary system is still in infancy, one hand the sound standard specification and uniform evaluation scheme has not yet established in the industry, on the other hand the prior art is difficult to achieve online state diagnostic of secondary system. In this paper, through analysis of status evaluation information sources and objects for secondary system, status evaluation index set and hierarchical model of smat substation secondary system were established. Further, the comprehensive status evaluation method of smart substation secondary system was established by fuzzy evaluation and gray clustering analysis and improved analytic hierarchy process. To ensure the reliable and accurate conversion of first system electric parameters in real-time, an online status diagnostic method of relay protection measurement circuit was put forward based on the fitted residual current. And the method can provide a theoretical reference for formulating scientific condition maintenance strategie of secondary system.Combined with background of security and economic operation & maintenance for smart substation secondary system, and according to the analysis of secondary system structural characteristic and secondary device functional role for smart substation, this paper comprehensive overview the present research situation of offline status evaluation and online status diagnosis. After collation and analysis of the relevant literature, this article raise existing defects and facing problems of status evaluation and hidden failure diagnosis for smart substation secondary system.For scientific and comprehensive evaluation of the secondary system operating state, the way to obtain online and offline state information based on operation&maintenance information management system and tegrated information platform were first proposed. According to the structure and functional characteristic of smart substation secondary system, the secondary system evaluation objects were established. Through characteristic analysis of operating state for secondary devices, and combined with operation&maintenance standard procedures and test technical specifications and existing research literatures, status evaluation index set and hierarchical model of secondary system were unified established.According to the established status evaluation index set and hierarchical model, first set up the scoring models of quantitative and qualitative indicator, and established the both state evaluation vector by fuzzy evaluation method and grey cluster analysis method, mainly include establishment of fuzzy membership functions for quantitative indicator and state evaluation sample matrix and grey clustering whitened weighted functions for qualitative indicator, and then built an evaluation matrix. Secondly, weight vector of evaluation object state indicators were calculated by the improved Analytical Hierarchy Process. Finally, based on the calculated status evaluation matrix and status index weight vector, comprehensive status evaluation result was calculated used of the weighted average model.For further monitoring online operating state of important secondary equipment, through analysis of error sources for protection current measurement circuit and error characteristic regarding the primary current and temperature, proposed the concept of residual current, established correlation function that inherent residual current on the primary current and temperature, and achieved the fitting of inherent residual current by artificial neural network, then put forward a online status diagnostic method of relay protection measurement circuit that based on the residual current fitting.